const s1=new Set( )
const s2=new Set(['a','b','c','b'])
s2.add('e').add('f').add('a')
let arr=[...s2]
console.log(s2);
console.log(s2.size);
console.log(arr);
s2.delete('c')
console.log(s2);
let flag=s2.has('c')
console.log(flag);
s2.clear()
console.log(s2);
s2.forEach(i=>console.log(i))